1. Field of the Invention
This invention relates to a diaphragm for a speaker, endurance against input of which is improved, particularly suitable for an on vehicle use and to a speaker device provided with the diaphragm.
2. Description of the Related Art
A cone speaker is most widely used among many types of speaker and used for a variety of purposes such as a television set, radio, on-vehicle system and hi-fi system.
FIG. 4 illustrates a basic structure of a conventional cone speaker, in which the central part is supported by a damper 44 and the peripheral part is supported by a frame 46 through an edge 45. Since the edge 45 functions as a spring to return a back-and-forth movement of the cone-type diaphragm 42, it is designed so as not to disturb an oscillation of the diaphragm. A voice coil 41, which is inserted in a magnetic gap of a magnetic circuit constituted by a magnet, plate and yoke, is applied with a current to oscillate the cone-type diaphragm 42, thereby generating a sound.
A neck of the cone-type diaphragm 42 is connected to the voice coil 41 by using an adhesive 43. Consequently, in response to a drive of the voice coil 41, a force in a direction of peeling the adhesive 43 off is always applied, causing a problem of endurance against input when a large volume is outputted from an amplifier (not shown in the figure). In some case, the adhesive is deteriorated to peel off, causing the diaphragm not to function.
Moreover, with use for a long period of time, the adhesive strength at the neck of the cone-type diaphragm 42 deteriorates, therefore the resonance sharpness of the crossover oscillation of the cone-type diaphragm 42 increases generating sharp maximum and minimum in the frequency characteristic, causing a disadvantage for obtaining a flat frequency characteristic in terms of audibility.
It is therefore an objective of the present invention to solve the above problem and provide a diaphragm for a speaker, endurance against input of which is improved.
It is another objective of the present invention to provide a speaker device, a frequency characteristic as well as the endurance against input of which are improved.
In order to attain the above objective, the present invention is to provide a diaphragm for a speaker comprising a convexo-concave portion radially formed at a neck of the diaphragm, the neck being. stuck to a voice coil bobbin.
The present invention is also to provide a speaker device provided with a diaphragm, a neck of the diaphragm being stuck to a voice coil bobbin, comprising a convexo-concave portion radially formed at the neck that is stuck to the voice coil bobbin by an adhesive.
Preferably, the diaphragm is a cone-type diaphragm.
Preferably, the convexo-concave portion is radially formed over the whole circumference of the neck.
Preferably, the cone-type diaphragm comprises: a first cone-shaped part moving in the direction nearer to the voice coil in a range from the neck up to a predetermined position of the diaphragm with respect to an oscillating direction of the diaphragm; and a second cone-shaped part moving in the direction away from the voice coil in a range from the predetermined position up to an edge of the diaphragm.
Preferably, the diaphragm is a plane diaphragm.
According to the construction described above, the convexo-concave portion is radially formed at the neck of the diaphragm for a speaker and the adhesive hardened in the convexo-concave shape is adhesively provided to the voice coil, to which the neck is connected, thereby an adhesion area of the neck is increased to increase the adhesive strength and the endurance against input is improved. Moreover, the mechanical strength of the neck of the diaphragm is increased, thereby the crossover resonance of the cone-type diaphragm is restricted and the frequency characteristic is improved.